I was searching through a friends "Following" list on Twitter today and as I was scanning the multitude of contacts I noticed my own picture in there. There's a nice little use of copy in the UI. Instead of just greying out the follow button to indicate that you can't follow yourself, you're told "That's you!".
The use of the exclamation mark even gives the impression that's it's a nice surprise to finding yourself in the list, and strokes your ego a bit at the same time.